Unit One Notes Cells – theory
THE FIRST OBSERVED CELLS • Robert Hooke (1665) – a British scientist who used a homemade microscope • Hooke looked at a piece of cork from the bark of an oak tree • It looked like the small rooms monks lived in at that time, so he named them Cellulae, which means “little room” in Latin • He could not see animal cells because they did not have a cell wall • Interesting fact – all known portraits of Hooke were destroyed in part because of an ongoing fued with Isaac Newton
SEEING CELLS IN OTHER LIFE FORMS • LEEUWENHOEK – IN 1673, THIS DUTCH MERCHANT WHO WAS INSPIRED BY HOOKE LOOKED AT POND SCUM UNDER THE MICROSCOPE. HE ALSO LOOKED AT GOOP SCRAPED OFF OF TEETH. • HE WAS THE 1ST PERSON TO SEE BACTERIA (CALLED THEM WEE BEASTIES), AND REALIZE THAT ANIMAL CELLS WERE DIFFERENT FROM PLANT CELLS
Cell Theory A fundamental idea of modern biology: • The three principles of the cell theory state: • All living organisms are composed of one or more cells • Cells are the basic unit of structure and organization of all living organisms (basic unit of life) • Cells arise only from existing cells, with cells passing copies of their genetic material on to their daughter cells. (cells make more cells)
Two Types of Cells • Cells come in different shapes and sizes based on the function they perform. • Cells have been grouped into 2 broad categories based on their internal structures: • Prokaryotic • Eukaryotic (these are generally 1-100x larger)
Two Major Types of Cells Prokaryotic Eukaryotic Cells without a nucleus Example: Bacteria Cells with a nucleus and other membrane bound structures. (Plant and animal cells)
Eukaryotic Cells Plant Cells Animal Cells Have Cell Walls A Large Vacuole Chloroplasts Have a Cell Membrane Small Vacuoles No Chloroplasts
Eukaryotic Cells cont. • Eukaryotic cells are larger and more complex • Have specialized internal structures – called organelles (like a nucleus) • Most multicellular organisms are eukaryotes (although some unicellular organisms like yeast are eukaryotes) • Eukaryotic cells have specialized functions (you have over 200 types of cells) • Believed to have evolved from prokaryotes; has led to cell diversity that helps organisms better adapt to their environments.